Stars and Blocks: Tailoring Polymeric Rheology Modifiers for Aqueous Media by Controlled Free Radical Polymerization

摘要

Associative telechelics, namely hydrophobically ?α,ω-end-capped water-soluble polymers, are particularly versatile and effective for the thickening or gelling of aqueous formulations. However due to the severe boundary conditions for the synthesis of water-soluble poly-mers, the synthetic options for associative telechelic polymers have been limited for long. A priori, classical free radical polymerization seems to be the most suited synthetic pathway for fabricating water-soluble polymers, also by virtue of the very large choice of the water-soluble monomers available. Yet, the inherent kinetics of the process do not allow for a reasonable control over the molecular structure or architecture. This situation has changed profoundly with the evolving methods of reversible deactivation radical polymerization RDRP (formerly often called "controlled free radical polymerization"). These methods enable an efficient and versatile control of molar mass, end-groups and polymer architecture. In order to exploit the possibilities of RDRP by straightforward one-step or two-step polymerizations without any further chemical transformation to prepare complex water-soluble polymers in general, and associative telechelics in particular, we have explored the use of the Radical Addition-Fragmentation chain Transfer (RAFT) technique in this context. The RAFT method is not only extremely versatile for introducing specific end-groups into polymers, but also enables inherently a rapid verification of the extent of end-group functionalization achieved.